Owing to the wide range of trigeneration systems suitable for small-scale applications, the selection of the optimal system according to the end users' requirements and environmental conditions is crucial. The evaluation and comparison of possible alternatives of trigeneration systems are a multi-criteria decision problem because not only economic aspects must be considered but also technical, environmental and social aspects. This paper presents the case of selection of a trigeneration system for a typical residential building. Several kinds of trigeneration systems, whose dynamical sources are Stirling engines, micro-turbines, reciprocating engines and fuel cells, respectively, and a separate generation system are evaluated and compared in detail. As the evaluation criteria are a mixture of quantitative and qualitative criteria, quantitative multi-criteria methods are inadequate for handling this type of problems. Therefore a multi-criteria decision-making method, which combines the subjectivity of decision maker and the objectivity of numerical data, based on Fuzzy Set Theory and Analytic Hierarchy Process is proposed to solve this selection problem. Copyright © 2010 John Wiley & Sons, Ltd.

After several decades, the incorporation of desalinated seawater into agricultural areas with scarce water resources has become one of the main water supply strategies. Compared to the several currently available desalination techniques, reverse osmosis (RO) is now the reference technology because it lowers energy uses and production costs. Nevertheless, its main limiting factor lies in the membranes used for this system not efficiently retaining boron, which is a problem because the concentration of this element in seawater is high. For 3 years, the present work analysed the impact of seawater temperature on the kinetic parameters of boron rejection in an RO system to establish their annual behaviour and the existing correlation between both parameters. A comparison was made using the values simulated in the projection software provided by the manufacturer of the membranes. The obtained results indicated a high correlation, and the R² correlation coefficients came very close to the unity. Nonetheless, this correlation lowered with time due to typical membrane ageing and compaction because of the system’s continuous operation. Under the tested working conditions and by applying analysed temperature intervals, it was impossible to reach the 0.3 mg·L⁻¹ boron concentration value that ensures lack of crop toxicity. Thus, incorporating other boron reduction techniques is necessary.

Today's challenges towards a sustainable energy development in most European nations are crucial and highly complicated. We find the need to choose between several technologies generation, whose task is very laborious. Multiple factors that affect the success of a Renewable Energy (RE) project must be analyzed and taken into account. The evaluation and comparison of possible technologies generation is a multi criteria decision problem because not only economic aspects must be considered but also technical, environmental and social aspects. This paper presents the case for selecting the optimal technology for electricity generation of 5 MW for a region located in the southeast of Spain. As most of the real-world multicriteria decision-making (MCDM) problems contain a mixture of quantitative and qualitative criteria; therefore discrete MCDM methods are inadequate for handling this type of decision problems.